Intra-aortic balloons (IAB's) are utilized to assist a weakened heart in the blood pumping function. The intra-aortic balloon is inserted into the body through the femoral artery for placement in the vicinity of the aortic arch. Since the femoral artery has a narrow diameter, it is important to provide a balloon having the smallest possible profile to facilitate entry and placement of the IAB. This has been accomplished through the development of the twistable balloon such as, for example, that described in copending application Ser. No.: 253,680 filed Apr. 13, 1981; which has matured into U.S. Pat. No. 4,422,477, dated Dec. 27, 1983. The intra-aortic balloon described in the abovementioned copending application is provided with an elongated stylet and operating means positioned external to the body for twisting the stylet in order to twist the balloon and cause it to be wrapped about the stylet, thereby significantly reducing the profile of the balloon and greatly facilitating its insertion into the femoral artery. Upon insertion and proper placement of the balloon, the operating means is rotated in the reverse direction causing the balloon to be untwisted and thereby placed in readiness for a balloon pumping operation.
The IAB is operated in synchronism with the operation of the weakened heart. In order to synchronize the operation of the IAB with the heart, it is conventional to employ an EKG signal which is derived by coupling a pair of electrodes, typically to the chest of the patient, which electrodes are coupled through conductors to an instrument which utilizes the R wave of an EKG for triggering balloon pumping. Instruments of this type also are provided with visual display means which make it possible to view the EKG signal and the balloon pumping signal to be assured of proper synchronism of the IAB with the heart and to monitor the progress of the balloon pumping operation.
The electrodes are typically coupled to the chest area of the patient. The electrical interface between the patient's body and the electrodes is of high resistivity, causing significant signal loss and erroneous signals through the interface. This decreases the integrity of the signal, and this condition is compounded by a weakened heart condition resulting in an EKG signal which is frequently insufficient for purposes of monitoring the heart and operating the IAB in synchronism with the pumping heart.
In addition, the "skin" electrodes are subject to erroneous signals complexes due to movement by the patient or disturbance of the electrodes by the medical procedure. These "false" signals may be incorrectly interpreted as "R-waves" and result in incorrect and harmful timing of the balloon.